What is OSHA terminology for a contaminated atmosphere that poses a severe threat to health?

The correct terminology used by OSHA for a contaminated atmosphere that poses a severe threat to health is "immediately dangerous to life and health." This designation indicates that exposure to the environment can lead to irreversible health effects or death within a short period. It emphasizes the critical need for immediate protective measures, such as using proper respiratory protection or evacuating the area.

Understanding this term is vital for first responders and workers in hazardous environments, as it defines the urgency of the situation and the necessary actions to protect health and safety. Other related terms may describe hazardous conditions but do not convey the same level of immediate danger or urgency associated with life-threatening exposure.